Plural duplex system of telegraphy



.May 11 1926.

F. E. DHUMY PLURAL DUPLEX SYSTEM OF TELEGRAPHY Filed July 18, 1924' 2 Sheets-Sheet 1 May 11 1926. 1,584,683

, F. E. DHUMY PLURAL DUPLEX SYSTEM OF TELEGRAPHY Filed July 18, 1924 2 Sheets-Sheet 2 Patented May 11, 1926.

T FEE.

FERNAND E. DHUMY, 0F ENGLEW'OOD, NEW JERSEY, ASSIGNOB TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PL'URAL DUPLEX SYSTEM OF TELEGRAPHY.

Application filed. July 18,

The present invention relates to duplex systems oftelegraphy.

'As commonly .used, duplex systems of the prior art utilize a single lineconductor together with a ground return circuit, and a balancing artificial line at each terminal station in which an efiort is made to duplicate the electrical characteristics of the line circuit in orderthat a perfect balance so far as possible, may be established. Owing to the external disturbances which affect the line circuit, and the ground potential variations at the grounded terminals, the extraneous current-s flowing in such lines are'at times of sufiicient magnitude to prevent the practical operation of the circuits. The ground currents become particularly troublesome during the occurrence of the a'uroraborealis and other atmospheric electrical disturbances, so that in certain installations the ground return must be replaced by a metallic return circuit. When this substitution is made, however, the disturbances induced in the line by induction still occur but are usually reduced in magnitude.

An object of the present invention is to provide a means whereby a plurality of such duplex circuits may be operated over one return conductor, instead of providing anindivi'dual return --wire for each of the duplex circuits. 4

By provi'dinga rtificial balancing lines of electrical characteristics which-' are proportional to. the values required to establisha balance rather than equal to the balancing values'as is the connnonpractice, and relying upon special winding arrangements in the return circuit to complete the balancing effect, and at-the same time to neutralize extraneous currents, an improved plural metallic duplex arrangement is provided with the addition of a single extra line. in this way, for two complete metallic duplex circuits only three line conductors are required. For three metallic circuits ordinarily six line conductors are required, but by the application of the present invention only four are needed. Accordingly, another object of the invention is to provide a plural duplex metallic circuit arrangement in which the number of conductors are reduced to a minimum.

ltis' found that by the application of the special windings and proportional artificial 1924. Serial No. 726,868.

line arrangements in grounded plural duplex systems, improved ground return systems are provided in which a balance maybe more readily effected and attained and in which increased operating currents are obtainable. A further object of the invention is therefore the provision of improved ground return systems without the addition Fig. '3 shows a metallic bridge duplex arrangement in which the principles of the invention are applied.

Referring to Fig. 1, the lines 1 are connected at their ends through coils 2 of diiferential receiving relays 8. Nindi'ngs lLof relays 3 are connected between points 5- of the line circuit and the artificial orbalancing lines 6. -Transm1tt1ng keys 7 are connected to points 5 and are adapted to connect one of the terminals of transmitting batteries '8 or other" sources of transmitting potential in 4 the "circuit. 3 The other terminals of batteries 8. and of artificial lines 6 are connected to a return conductor 9 at points 10, and windings 11 applied to relays 3 are connected in series in. conductor 9. On the'back contacts keys 7 complete metallic circuits through branches 1:? to points 1O. I w

The windings 2 and 4 are arranged so that transmitted currents passing outward from points 5 over winding 2 to line 1 willset up in agneto-motive forces which will be opposed by the magneto-motive forces set up by the currents passing outward from points 5 through windings 4i and artificial lines 6, while incoming currents will pass around windings 2 and i in well known manner to cause the magneto-motive forces caused thereby to add. The constants of artificial lines 6 are proportional but not equal to the main line constants or the constants necessary to establish a balanced'condition, so that more current will passthrough windpolar system with two differential duplex lines.

ings t than will pass through windings 2 with a result that the magnetic forces deveL oped by transmitted currents in these windings will notbalance. The windings 11 on relays 3 are, however, so proportioned and arranged that the magnetic eficct thereof due to the returning currents, will be added to the magnetic effect of windings 2 in a manner to balance the magnetic etlects of the transmitted impulses. It will be noted that for the received impulses, the direction of current in windings 2, 4 and 11 are such that the magneto-motive forces are added, and the result is an increased pull on the receiving relay over and above that which may be obtained using ordinary two coil differential relays.

In operation, for transmittel currents at any station, the effect of wind ngs 2 and 11 will balance the effect of winding 4; but for received currents the elfects of windings 2, 4 and 11 will be added to operate the relays 3, and duplex transmission may be carried on simultaneously over each line circuit 1. It will be apparent that a plurality of metallic return paths are provided in this arrangement with the addition cf only one extra line, and for this reason, for the same values of applied potential higl er operating currents are available than in slngle metallic duplex systems. For two duplex circuits on three line conductors a ratio of main circuit to artificial circuit constants of 3:2 will give excellent results; for three circuits on four conductors a ratio 4:3 may be used; for four circuits on five conduct rs the ratio may be 5:4 and so on, but it w ll be understood that these values may be aried within wide limits and the proportions of the relay windings may be varied accordngly.

In Fig. 2, a plural duplex arrangement using impulses of opposite polarities and polarized receiving relays is shown. The only change over the form shown in Fig. 1 is in the addition of suitable transmitting batteries 14 in the branches 12 so that when the keys 7 are open, potentials of a polarity opposite to the potentials when the keys are closed will be applied to the line. The proportions, arrangement and operation are readily understood from the dtscription in connection with Fig. 1 and need not be repeated here.

The invention is applicable to bridge duplex systems and such an arrangement is shown in Fig. 3. The receiv ng relays 15 have windings 16 thereof connected in a bridge between line 1 and art ficial line 6, and windings 17 thereof are connected in series in return conductor 9. The ends of 9 are connected at points 10 between the artificial lines 6 and the batteries 8. Artificial lines 6 have electrical characteristics which are proportional to but not equal to the characteristics of the corresponding main circuits, as above set forth, so that when signals are transmitted, an unlalanced current will flow from through th winding 16 of the home relay. indings 17 in line 9 are, however, so proportioned and arranged that the magnetic effect of this unbalanced flow in windings 16 will be compensated by the flow of the returning current in line 9. Because of the wide difference in characteristics of the main and balancing circuits, the unbalanced currents will always flow in the same direction through windings 1G, and windings 17 may be properly designed to compensate therefor. For the received currents, the magnetic effect of windings 16 and 17 will add, and the relays will respond in accordance therewith.

By grounding the return line 9 at each station after it has passed through windings 11 in Figs. 1 and 2, or windings 17 in Fig. 3, the section of conductor 9 between the stations may be eliminated and an in'iproved ground return system is provided using the proportional artificial lines and return circuit compensating windings.

Having described preferred embodiments of the invention, what is desired to be secured by Letters Patent and claimed as new is:

1. The method of operating a duplex system which comprises establishii g a definite unbalanced condition in the hcme receiving relay, and compensating for the unbalanced condition by the current flowing in the return circuit of the system.

2. A duplex system comprising a main line circuit, and an artificial line r-rcuit maintained in definitely unbalanced relation with respect to said main line circuit 3. A duplex system compris ng a main line, an artificial line maintained in definitely unbalanced relation with respect to said main line, and a return circuit for said main line.

4. The system as set forth in claim 3 together with a relay having a winding connected in said return circuit.

5. The system as set forth in claim 3 in which said return circuit is entirely metallic.

6. The system as set forth in claim 3 together with a relay having a winding in series with said main line a wind ng in series with said artificial line, and a winding in series in said return circuit.

7. A duplex system comprislrg a pluralitv of main line conductors, artificial lines individual to said main line conductors, a common return circuit for said main line conductors, electro-resnonsive receiving means individual to each of said main line circuits and a winding indiv dual to each of said receiving means mounted in said return circuit, said return circuit being entirely metallic and said winding being'connected in series therein.

8. A duplex system of telegraphy comprising a main line. an artificial line having impedance diflerent from that of said main line a receiving relay having a plurality of windings, two of said windings connected in series respectively with the main line and another winding connected with the artificial line, said windings being arranged in such a manner that the magnetic pull developed in the relay from a given received current is greater than the magnet c pull developed in a two-equal-coil diffe=ential relay by an equal received current.

In testimony whereof I affix my signature.

FERNAND E DI-IUMY. 

